In semiconductor manufacture, during the manufacturing process, wafers are sequentially processed in a plurality of process steps, wherein a plurality of similar, repetitive structural elements, the so-called dies, are produced on a wafer. As integration densities increase, the requirements as to the quality of the structures formed on the wafer become ever more demanding. To be able to verify the quality of the structures formed and to find defects, if any, the requirements as to the quality, the precision and the reproducibility of the components and process steps for handling the wafer are correspondingly stringent. This means that in the production of a wafer comprising a great number of process steps and with the great number of layers of photoresist or the like to be applied, the reliable and early detection of defects in the individual structures or structural elements is particularly important.
German patent application DE 103 07 358 discloses a method and apparatus for scanning a semiconductor wafer. On-the-fly images of areas on the wafer are taken by a camera. When the scanning line is changed, a continuously curved translation path is created by at least partially superimposing the relative movement between the wafer and the camera in the direction of the scanning line and normal to it. This serves to save time and to increase wafer throughput.
German patent application DE 103 07 373 discloses that depending on the size of the stepper and die (design) the size of the SAW varies greatly. Generally it cannot be expected that a SAW can be recorded with a single camera image. A SAW is therefore subdivided into portions (segments) of equal size. Each logical SAW segment is associated with a SAW index. The images of the individual SAW segments are stored in a memory and can be retrieved from there by making reference to the index.
US Patent Application. US 2004/0047501 discloses a visual inspection device and method. The chips on the wafer are arranged in lines and subdivided into groups. The images of the chips of a group are compared with each other. If a group contains three chips, this means that the first chip is compared with the third chip, the first chip is compared with the second chip, and the second chip is compared with the third chip. In parallel to this, images are continued to be obtained. The analysis of the images is limited to an analysis of the images of one scanning line. Moreover, the detection of defects in the edge area of a wafer is not possible.